Irbesartan is chemically described as 2-butyl-3-[[29-(1H-tetrazol-5-yl) [1,19-biphenyl]-4-yl]methyl]1,3-diazaspiro[4,4]non-1-en-4-one, also as 2-n-butyl-4-spirocyclopentane-1-[(2′-(tetrazol-5-yl)biphenyl-4-yl)methyl]-2-imidazolin-5-one, also as 2-butyl-3-[[2′-(1H-tetrazol-5-yl)[1,1′-biphenyl]-4-y]methyl]-1,3-diazaspiro[4,4]non-1-en-4-one. Its empirical formula is C25H28N6O, and it has the following structure:

Irbesartan has a molecular weight of 428.5. The compound is described in U.S. Pat. No. 5,270,317, which is incorporated herein in its entirety.
In the United States, irbesartan is available for oral administration tablets containing 75 mg, 150 mg, or 300 mg of irbesartan, which are sold under the trade name AVAPRO. The drug also is formulated as 150 and 300 mg tablets that also include 12.5 mg hydrochlorothiazide, which are sold under the trade name AVALIDE.
As noted in U.S. Pat. No. 6,342,247, irbesartan is a fluffy material with relatively low bulk, and tap densities. In addition, irbesartan has certain undesirable flow characteristics. These properties make it difficult to formulate a large amount of the drug into a small tablet. Indeed, the '247 patent describes an oral formulation of irbesartan containing only up to 70% of the drug. Accordingly, there is a need for an improved formulation of irbesartan that contains a higher amount of the active ingredient.